This project is concerned with axoplasmic organelles containing sodium and potassium ion channels which are transported along the axon via neurofilaments to various points where they fuse with the axonal membrane, thereby inserting ion channels which underlie excitability in the membrane. We have recently found that the organelles can be separated on the basis of size into anterograde and retrograde fractions via control- pore-size glass bead chromatography. We are currently investigating these two fractions with transmission electron microscopy and SDS polyacrylamide gel electrophoresis. We are also investigating the ion channels contained in each fraction by incorporating the organelles into artificial lipid bilayers and using the voltage-clamp technique to characterize the ion channels electrophysiologically.